Piston for an internal combustion engine

ABSTRACT

The invention relates to a piston for an internal combustion engine, comprising an essentially cylindrical basis member made of forged aluminum and a ring element that is disposed in the radially outer edge area of the bottom of the piston and forms an annular cooling channel along with the basic member. The ring element is made of cast aluminum and is provided with a ring support for a compression ring, said ring support being made of Ni-resist.

The invention relates to a piston for an internal combustion engine, inaccordance with the preamble of the claim.

A piston for an internal combustion engine, having a basic body made ofaluminum and a ring element disposed in a radially outer edge region ofthe piston head, which ring element forms a ring-shaped cooling channelwith the basic body, is known from U.S. Pat. No. 2,772,933. The ringelement consists of an iron alloy, which brings the disadvantage with itthat the ring element makes a significant contribution to increasing thepiston weight.

It is the task of the invention to avoid this disadvantage. This task isaccomplished with the characteristics that stand in the characterizingpart of the main claim. A practical embodiment of the invention is theobject of the dependent claim.

The ring element which, according to the invention, consists ofaluminum, having a ring insert consisting of Ni resist, for acompression ring, combines the advantage of reducing the piston weightwith the advantage of offering a wear-resistant bearing for thecompression ring, and thereby increasing the ability of the piston towithstand stress, and its useful lifetime.

An exemplary embodiment of the invention is described below, using thedrawings. These show:

FIG. 1 a piston for an internal combustion engine, having an aluminumring element according to the invention, in a sectional drawingconsisting of two halves, which drawing shows two longitudinal sectionsof the piston, offset by 90°, and

FIG. 2 an enlarged representation of the section through the edge regionof the piston head having the ring element.

FIG. 1 shows a piston 1 for an internal combustion engine, in asectional representation that consists of two halves, of which the lefthalf shows a section of the piston 1 along a longitudinal axis 2 of apin bore 3, and the right half shows a section through the piston 1 thatis offset by 90° relative to the left half.

The piston 1 consists of an essentially cylindrical basic body 4, theone face of which forms the piston head 5. A ring element 6 is disposedin the radially outer region of the piston head 5. A combustion chamber7 is molded into the central region of the piston head 5. Furthermore,the basic body 4 has pin bosses 8 for the pin bores 3 and skirt elements9 that connect the pin bosses 8 with one another, on its underside thatfaces away from the piston head 5. The ring element 6 has a ring insert11 for a compression ring, not shown in the drawing, on its radiallyouter mantle surface 10, and a second ring groove 12 below this. Belowthe second ring groove 12, an oil ring groove 14 is disposed in themantle surface 13 of the basic body 4.

The ring element 6 is attached on the basic body 4 by way of a screwconnection, in which the ring element 6 is screwed onto an outsidethread 18 by way of an inside thread 19, which is situated on theradially inner side of the ring element 6, which outside thread isdisposed on an axially oriented region 23 of the mantle surface 13,which is adjacent to the piston head 5 and is set back in the directionof the longitudinal axis 17 of the piston.

The radially inner side of the ring element 6 has a recess 20 on itslower end that faces away from the piston head 5, which recess forms aring-shaped cooling channel 22 with a recess 21 that is molded into thelower end of the set-back mantle region 23 on the piston head side.Cooling oil is passed into the cooling channel 22 and back out of thecooling channel 22 by way of channels not shown in the figure.

In order to prevent combustion gases, which are under high pressure,from getting into the cooling channel 22 and into the interior of thepiston by means of the screw connection 18, 19, the end of the screwconnection 18, 19 that is on the piston head side is sealed by means ofa weld seam 24, which can be produced, for example, using the electronbeam welding method.

The piston 1 that consists of the basic body 4 and the ring element 6 isproduced from aluminum, whereby the basic body 4 is given the desiredshape by means of forging, whereas the ring element 6 is produced usinga casting method. In this connection, the ring insert 11, which consistsof Ni resist (austenitic cast iron with components of Ni, Mn, Cu, andCr), is cast into the ring element 6. After the ring element 6 has beenscrewed onto the basic body 4, and the screw connection 18, 19 has beensealed by means of the weld seam 24, the piston 1 is given its finalshape by means of a cutting production process, for example by means oflathing.

The section through the edge region of the piston 1 on the piston headside, shown in FIG. 2, shows the ring element 6 having the cast-in ringinsert 11, which is connected with the basic body 4 by way of the screwconnection that consists of inside thread 19 and outside thread 18. Theweld seam 24 that serves to seal the screw connection 18, 19 can beclearly seen.

REFERENCE SYMBOLS

-   1 piston-   2 longitudinal axis-   3 pin bore-   4 basic body-   5 piston head-   6 ring element-   7 combustion chamber-   8 pin boss-   9 skirt element-   10 mantle surface-   11 ring insert-   12 second ring groove-   13 mantle surface-   14 oil ring groove-   17 longitudinal axis of piston-   18 outside thread-   19 inside thread-   20 recess-   21 recess-   22 cooling channel-   23 region of the mantle surface of the basic body 4-   24 weld seam

1. Piston (1) for an internal combustion engine, having an essentiallycylindrical, forged basic body (4) made of aluminum, whose one faceforms a piston head (5), having pin bosses (8) with pin bores (3)disposed on the underside of the basic body (4) that faces away from thepiston head (5), having skirt elements (9) that connect the pin bosses(8) with one another, having a ring element (6) disposed in the radiallyouter edge region of the piston head (5), which forms a ring-shapedcooling channel (22) with the basic body (4), wherein the ring element(6) consists of cast aluminum and has a ring insert (11) for acompression ring, that the ring element (6) is connected with the basicbody (4) by way of a screw connection that consists of an inside thread(19) disposed on a side of the ring element (6) that lies radiallyinside, and an outside thread (18) that matches the former, disposed inthe region of the mantle surface (13) of the basic body (4) on thepiston head side, and that the end of the screw connection (18, 19) onthe piston head side is sealed by means of a weld seam (4).
 2. Piston(1) for an internal combustion engine according to claim 1, wherein thering insert (11) consists of Ni resist.